This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. Ribonucleotide reductases are the sole source of deoxyribonucleotides in the cell and are thus vital for all living cells. While there are multiple classes of RNR's the E. coli class I enzyme has been extensively studied. The reaction requires two proteins, the active site containing [unreadable] and the radical generating protein [unreadable]. The [unreadable] protein provides a radical to the active site of [unreadable], required for catalysis. While structures of the two subunits are known, there is no available structure of [unreadable] and [unreadable] in complex and the oligomerization state is not well known. We are attempting to obtain a structure of [unreadable] and [unreadable] in complex to begin to address some of the issues unresolved by biochemical and biophysical methods used so far.